The object of this study is to make clear the relation between the shape of
balcony and acoustical properties under the overhang, and to derive a design
criterion for balcony configuration in auditoria. On the assumption that a
physical change of the sound field caused by building a balcony would be
primarily a reduction of the energy of early reflections from upside,
directional characteristics of early reflections were measured in auditoria both
with and without a balcony, and the subjective effect of reflections arriving
from upside on auditory envelopment was psycho-acoustically examined. First, the
results of measurement showed that the ratio of the vertical component to total
early reflection energy ER[inf V] was very small under the overhang. That is a
peculiarity of the sound field under the balcony. Next, the results of a series
of psychoacoustical experiments showed that auditory envelopment became weaker
as ER[inf V] decreased when lateral energy fraction was constant. They suggested
that the lack of early reflections from the ceiling above the main orchestra
causes the peculiarity of directional distribution of early reflections, and
consequently disturbs auditory envelopment under the balcony.